1. Field of the Invention
The present invention relates to an environment recognition device and an environment recognition method for recognizing a target object based on luminances of the target object in a detection area.
2. Description of Related Art
Conventionally, a technique has been known that detects a target object such as an obstacle including a vehicle and a traffic light located in front of a subject vehicle for performing control to avoid collision with the detected target object and to maintain a safe distance between the subject vehicle and the preceding vehicle.
In this technique, stereo matching processing is performed an image of an environment ahead of a vehicle captured by two cameras, for example, in order to derive parallax for each block including a predetermined number of pixels. Based on this parallax, a position of the vehicle in thereat world is derived.
There is also a technique that performs more advanced control. Specifically, it not only specifies a target object uniformly as a solid object, but further determines whether the detected target object is a preceding vehicle that is running at the same speed as the subject vehicle or a fixed object that does not move. For example, there has been proposed a technique in which a point detected as being tilted at a predetermined angle with respect to the advancing direction of the subject vehicle is determined as a wall such as a guard rail, while a point detected along the horizontal direction of a plane vertical to the advancing direction of the subject vehicle is determined as a back surface of a preceding vehicle (for example, Japanese Patent. Application Laid-Open (JP-A) No. 2008-59323).
However, for example, when light of a tail lamp is diffused at night or in rainy weather, a block that does not indicate the tail lamp might erroneously be matched with a block indicating the tail lamp in the stereo matching process. In this case, the position of the tail lamp, which is derived from the mismatching, in the real world is recognized as being tilted at a predetermined angle with respect to the advancing direction of the subject vehicle. By virtue of this, the portion that are supposed be determined to be the back surface of the preceding vehicle might be determined to be a wall in the technique described in JP-A No. 2008-59323. When an object determined to be a wall is detected in the advancing direction, automatic control for performing an avoiding operation, which is originally unnecessary, might be executed.